Clutch



Nq'v. 21, 1939. E. R. HA RT 2,180,412

CLUTCH Filed Feb. 5, 1937 INVENTOR.

EARL R. HART. I BY ATTORNEY.

' winding 4 having a relatively large central 'cylin drlcal-opening 5, is placed within thehousing sub- Patented Nov. 21, 1939 UNITED STATES CLUTCH e 1 Earl R. Hart, Cleveland Heights, Ohio; assignor o The' Clark Controller Company, Cleveland,

Ohio, a corporation of Ohio e I Application February 5, 1931, Serial No. 124,285

'3 Claims. (01. 192- 4) 7 This invention relates to clutches and particularly to electro-magnetic clutches for clutching together a pair of rotatable elements.

It is among the objects of the invention: H

To provide generally an improved electro-magnetic clutch.

To provide an electro-magnetic clutchhaving improved means for preventing sticking of the engaged clutch elements by residual magnetism.

-To provide an improved construction of mutually engageable clutch elements, permitting driving of one clutch element by the other when r they are rotatably mounted on axes that .are not in alignment. To provide an electro-magnetic clutch having the minimum number of parts and in which adhesion of the magnetically attracted parts due to residual magnetism is prevented, and frictional engagement of the clutch elements is effected and relative universal joint movement of the engaged clutch elements is provided.

Other objects will be apparent to'those skilled in the art to which my invention appertains:

My invention is fullydisclos'ed in the following I description taken in connection with the accompanying drawing in which: r e r Fig. 1 is a longitudinal sectional'view illustrat ing an embodiment of the clutch of my invention associated with an electro-magnetic winding for engaging the clutch and a housing for the parts thereof;

Fig. 2 is a longitudinal elevational view of the clutch elements proper of Fig. 1. Figs. 3, 4 and 5 are fragmentary views illustrat ing modifications of some of the parts of Figs. 1 and 2. I Referring to the drawing I have shown at ll a pair of frame members spaced apart and connected by a tubular frame member 2, the-opposite axial ends of which are seated in annular recesses 33 in the frame members |--l. parts l-l and 2 together, the frame-members |I may be clamped upon the tubular member 2 by means not shown or may be otherwise secured thereto but preferably one or both-of theframe members ll maybe removedfrom'the'end of the tubular member 2 to give access to the interior of the member 2. An electro-magnetic stantially fitting between the two end frame members ll and is supported co-axially of the tubular member 2 by retainers 66 preferably of circular disc form substantially fitting at their peripherieswithin the cylindricalopening 5'of To secure the the winding. The retainers 6 maybe supported on "the frame members l-l by any suitable means but Iprefer to form-them as flanges integral with tubes 'Il, the latter being projected through suitable bores 8-8 in the'frame members 5 The tubes 1-1 have, telescoped into the bores thereof, sleeve-type bearings 9--9 disposed in coaxial alignment and apair of shafts l0 and'l I are rotatably supported in the bearings 9.9 in sub- 10 stantially co-axial alignment. 1

Either. one of the shafts l0 and ll may be the driving shaft and the .other the drivenshaft but I prefer to apply power to the shaft l0 and to transintegrally therewith. The heads and I3 and 20 preferably therefore also the shafts Ill and ll are formed from ferrous material.

'"Theheads- I2 and .3 are provided respectively with faces and I5 preferably in'planes at right angles to the rotational axis of the shafts and in 2 5 the medial plane of the winding 4.

As will now be apparent, when the winding 4 is electrically-energized magnetic flux will be cre-' ated in the magnetic-circuit comprising the two heads I2 and I3, the air gap l6 between the faces 30-- II and 15, the two shafts land I I, the frame elements I-l and the tubular frame member 2, and the flux in the gap IE will attract the heads l2 and I3 toward each other. The shaft I0 is preferably anchored against longitudinal movement by 35 a shoulder I'l onl'the shaft engaging the inner end of the corresponding sleeve bearing 9 and by a gear [8 (or other mechanism element or power supplyingelement) on the shaft Ill engaging the outer end of the bearing 9. r

The head l3 and shaft H however are axially movable in the direction to reduce the thickness of the air-gap It. The shaft H is normally retained toward the rightjas viewed in the drawing to provide the maximum air-gap 'l6'by a spring 19 abutting at one end upon a thrust washer 20 encircling the shaft and engaging the outer end of the corresponding bearing 9 and abutting at its other end upon a thrust washer 2| engaging a collar 22 secured to the shaft II in any suitable manner, for example by a pin 23. The outward movement of the shaft is determined by a shoulder 24 on the shaft engaging the inner end of the corresponding bearing 9.

The spring I9 is preferably so proportioned 56* that it will be compressed when the shaft II is moved inwardly or toward the left as viewed in the drawing and so that when the shaft II is moved toward the right by expansion of the spring, the spring will have expanded to its full length and will therefore be without tension when the shoulder 24 is approximately in engagement with the end of the bearing 9 so that in this normal position of the parts there will be substantially no pressure at the shoulder 24 nor at the thrust washers 20 and 2|.

The head I3 is provided, on the axially inner portion thereof with an annular convex rounded surface 25. The head I2 has mounted thereon a sleeve 26 of non-ferrous or non-magnetic material formed with a concave conical surface 21 confronting the surface and normally spaced therefrom. The surfaces 21 and 25 are both preferably co-axial of the shafts Ill and II. v

The sleeve 26 may be secured upon the head I2 in any suitable manner but preferably is telescoped on a reduced diameter portion 28 and abuts upon a shoulder 29 thereof to position it and the fit of the sleeve on thereduced diameter portion 28 is preferably a press-fit so that the sleeve will not rotate relative to the head.

The space or gap 30 between the annular surfaces 25 and 21 is smaller axially than the magnetic air-gap I6. I

In the operation of the device above described, the shaft I may be rotated, for example by means of the gear I8 and the shaft II will be at rest. To drive the shaft II, the winding 4 is energized. Thereupon the magnetic attraction effected by the flux in the air-gap I6 in the magnetic circuit above described will draw thehead I3 toward the head I2 compressing the spring I9. The surface 25 will engage with the surface 21 before the faces I4 and I5 meet thus maintaining a reduced airgap ISA. The force of the attraction will frictionally engage the surfaces 25 and 21 and the shaft I I will thereby be driven. Although the parts above described may be constructed with the intention of causing the shafts I0 and II to be in axial alignment, exact axial alignment is diflicult and expensive to attain; and in all clutches of this general class, and even when manufactured by approved heads such as the heads l2 and I3 actually en-' gage upon magnetic surfaces, in a plane at right angles to the axis of rotation, even a very slight degree of mis-alignment of the shafts, causing such faces to engage at a point on one side of the axis, will cause the magnetic attraction to tend to bend the shafts in their bearings and to cause them to bind therein, creating excess friction and wear. With the arrangement illustrated and above described however, providing the concave conical surface 21 and the convex rounded surface 25, and maintaining, at all times, an airgap I6A, these defects of clutches of this general class are completely obviated. If the shafts are out of alignment the surfaces 25 and 21 will make contact with each other on at least a point and one head will roll on and drive the other somewhat in the nature of engaged gears, and both shafts will rotate freely in their bearings. The rolling contact engagement of these surfaces will be maintained by the magnetic pull, and the driveof one by the other will be madecertain v and relatively little friction,

at varying amounts of axial mis-alignment by the wedging character of the engagement of the surfaces due to the inclined conical surface on one head and the rounded convex surface on the other head.

From the foregoing, it will now be apparent that the element 26 performs three distinct functions. It provides one of the two surfaces 21 and 25 which are frictionally pressure engaged by the magnetic attraction to effect a clutching of the two heads I2 and I3 together; and it provides one of the surfaces through which when the two heads I2 and I3 are so engaged, one may drive the other without binding in the bearings; and it also provides a non-magnetic gap to prevent actual contact engagement of the magnetic parts of the heads I2 and I3 which, because of the principle of residual magnetism, would cause these parts to stick together when the winding is de-energized.

Upon de-energizing the winding v4, the spring I9 withdraws the head I3 thus breaking the clutching engagement of the heads and transmission of power-to the shaft II ceases. Since the gap ISA is maintained and residual magnetism cannot cause sticking, the spring I9 may be a relatively weak spring and therefore during such time as the heads are clutched together and the spring I9 is under compression, it causes small pressure at the thrust washers 20 and 2| sfnall wear and loss of power thereat.

As stated above, the spring I9 is preferably so proportioned that when it has retracted the shaft II. to-its normal clutch-disengaged position, it will have substantially no tension therein. By this means, the ampere turns excitation of the winding 4 is reduced to the minimum because, as is well known, when an air gap, such as the air gap I6, is of substantial length, which in this instance is the case, when the heads I2 and I3 have been retracted, the magnetic pull is very much weaker than when the gap has been shortened by movementof the head I3 toward the head I2. The winding 4 must supply sufficient flux and pull to start the head I3 to move, and if the spring I9 is without tension at this time, a relatively small excitation of the winding will be sufficient to start the head I3. After the head I3 starts to move and the gap I6 reduces in length, the rapidly increasing magnetic pull can overcome the increasing tension of the spring I9. The result is that the head I3 canbe movedinto engagement with the head I2 with a smaller excitation in the winding 4 if the spring is without tension at the start of the pull.

Furthermore, as stated above, if desired the shaft II may be the driving shaft and the shaft III the driven shaft, and in such cases, the shaft II will rotate idly during periods of time when the clutch is. not engaged and if, in such cases, the spring I9 were under tension there would be constant wear at the thrust washers 20 and 2|, but by providing the spring I9 without tension when the head I3 "is in its retracted position, such continuous'wear is avoided.

The arrangement of the surfaces 21 and 25 illustrated is the preferred arrangement. However, it is believed to be apparent, that the conical surface may be on the head I3 and the round ed surface on the head I2 as shown for the rounded surface 25a and the conical surface 21a, in Fig. 3, or that the surface on the head I2 may be the magnetic surface and the surface on the head I3 the non-magnetic surface as shown for the surfaces 25a and 21a respectively, in Fig. 3, and as also shown for the surfaces 25b and 2Ib, of Fig. 4. Similarly, while I have shown in Figs. 1 and 2, one surface conical and the other a rounded annular surface, it will be apparent that both surfaces may be conical at slightly different angles as shown for the surfaces 250 and 210 of Fig. 5 or that both may be'rounded, one concave and the other convex. In general, therefore, it may be said that the principles of the invention may be practiced with surfaces 21 and 25 which are generally'frusto-conical, one concave and the other convex, and nested one within the other; and this term, frustoeconical, in

the claims is used in this broad sense to be in-- clusive of all such arrangements.

In Figs. 3, 4 and 5, the heads [2 and Bare illustrated in their clutch-engaged positions.

It will be apparent therefore that my invention is not limited to the exact details of construction illustrated and described and that numerbus changes and modifications may be made within the spirit of my invention and without sacrificing its advantages and within thescope of the appended claims.

I claim:

1. In a. magnetic clutch, a pair of rotatably supported ferrous clutch elements, having confronting surfaces providing a magnetic air-gap I therebetween, an electro-magnetic winding dis- 7 posed to cause, when energized, magnetic flux to flow through the air-gap to exert mutual magnetic attraction of the clutch elements, an element of non-ferrous material secured to one clutch element and having an annular substantially frusto-conical friction surface thereon, a corresponding annular convexly rounded friction surface on the other clutch element, the'magnetic attraction causing the said surfaces tofrictionally engage to effect a driving connection between the clutch elements, and the non-ferrous element maintaining the said air-gap to reduce residual magnetism when the winding is de-energized. V

2. In a magnetic clutch, a pair of rotatably supported ferrous clutch elements, having confronting surfaces providing a magnetic air-gap therebetween, an electro-magnetic disposed to cause, when energized, magnetic flux to flow through the air-gap to exert mutual ma netic attraction of the clutch elements, an eleclutch elements, and the non-ferrous element maintaining the said air-gap to reduce residual magnetism when the winding is lie-energized.

3. In a magnetic clutch, a main frame, a pair of rotatably supported ferrousclutch elements on the frame, one of which is axially movable, the elements having confronting surfaces providing a magnetic air-gap therebetween, an electromagnetic winding disposed to cause, when energized, magnetic flux to flow through the airgap to exert mutual attraction of the clutch elements, an element of non-ferrous material secured to one clutch element and having an an-,

nular substantially frusto-conical friction sur- 5 face thereon, a corresponding annular substantially frusto-conical'friction surface'on the other clutch element, one of said flllStO-COIllGfiJSllI- faces being concave and the other being convex,

'the magnetic attraction causing said axially movable element to move to cause the said surfaces to frictionally engage to effect a driving connection between the. clutch elements, the nonferrous element maintaining the said air-gap to reduce residual magnetism when the winding is de-energized, a spring effecting axial thrust upon the frame and said axially movable ele-- ment to eifect retraction of the axially movable element and dis-engagement cf the clutch ele- 'ments when the winding is de-ener'gized, and the spring being proportioned to be substantially without tension when the said element is retracted to avoid thrust effected wear during rotation of the axially movable element in its retracted position. a

-' EARL R. HART. 

